Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$184.60	3.379%	$190.8376	$190.84	$190.85	$190.80
Purchase #2	$170.52	9.246%	$186.2863	$186.29	$186.30	$186.30
Purchase #3	$147.95	9.703%	$162.3056	$162.31	$162.30	$162.30
Purchase #4	$71.95	3.599%	$74.5395	$74.54	$74.55	$74.50
Purchase #5	$27.40	13.600%	$31.1264	$31.13	$31.15	$31.10
Purchase #6	$138.46	13.148%	$156.6647	$156.66	$156.65	$156.70
Purchase #7	$237.26	11.425%	$264.367	$264.37	$264.35	$264.40
7 purchase totals =	$978.14		$1,066.1271	$1,066.14	$1,066.15	$1,066.10